The present invention relates to fluid pressure actuated force generating pistons that only have a non-metallic contact with the metallic cylindrical housing walls. This invention is particularly useful in the aircraft wheel and brake art because of its high reliability and long interval between maintenance. The aircraft brakes use multiple frictional surfaces and it is desired to have the piston assemblies perform as long as the frictional material, without maintenance. The preferred embodiment is designed to fit in an aircraft wheel disc brake assembly as generally shown in U.S. Pat. Nos. 3,403,759 and 2,888,101, however, the piston assembly of the present invention is not necessarily restricted to this field.
All prior art known to the applicant provide some metal-to-metal contact between the sliding surfaces which cause wear and subsequent seal leakage. The present invention eliminates the metal-to-metal sliding surfaces thereby decreasing wear and increasing the operable life of the piston and housing, yet, utilizes and retains the advantages of metallic sealing surfaces.